1. Field of the Invention
2. Description of Related Art Image-guided surgery system The invention relates to an image-guided surgery system which includes a position measuring system for measuring a position of an instrument.
An image-guided surgery system of this kind is known from the U.S. Pat. No. 5,389,101.
An image-guided surgery system is used to display a position of a surgical instrument in an operating zone within the body of a patient to a user, for example a surgeon, during a surgical intervention. Images of the patient, for example CT or MR images, are formed prior to the operation. The image-guided surgery system includes a position measuring system for measuring the position of the surgical instrument. The image-guided surgery system also includes a computer for deriving corresponding positions in a relevant image from the measured positions of the surgical instrument. During the operation the position measuring system measures the position of the surgical instrument relative to the patient and the computer calculates the position in such a previously formed image which corresponds to the measured position of the surgical instrument. A monitor displays the previously formed image in which the actual position of the surgical instrument is reproduced. The image on the monitor shows the surgeon exactly where in the operating zone the surgical instrument is located, without the surgeon having a direct view of the instrument. The image displayed on the monitor thus shows the surgeon how to move the surgical instrument in the operating zone without high risk of damaging of tissue and notably without risk of damaging of vital organs.
An image-guided surgery system of this kind is used, for example in neurosurgery in order to show the surgeon exactly where the surgical instrument is located in the brain during cerebral surgery.
The known image-guided surgery system can be used only if the dimensions of the instrument are accurately known already. The instrument is provided with light-emitting diodes (LEDs) which emit light which is detected by the position measuring system so as to measure the position of the LEDs. The position of the LEDs on the instrument, relative to an end of the instrument, must be constant and accurately known so as to enable the position of the end of the instrument to be accurately derived from the measured positions of the LEDs on the instrument.